AP BIOLOGY

Detailed explanation-1: -Respiration involves the following steps: (i) Breathing or pulmonary ventilation by which atmospheric air is drawn in and CO2 rich alveolar air is released out. (ii) Diffusion of gases (O2 and CO2) across alveolar membrane. (iii) Transport of gases by the blood.

Detailed explanation-2: -During gas exchange oxygen moves from the lungs to the bloodstream. At the same time carbon dioxide passes from the blood to the lungs. This happens in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.

Detailed explanation-3: -Once the venous blood returns to the lungs, the carbon dioxide diffuses out of the bloodstream, through the capillaries, and into the alveoli from where it is expelled, during which time oxygen simultaneously binds with hemoglobin to be carried back to the tissues.

Detailed explanation-4: -Gas Exchange Between Alveolar Spaces and Capillaries Three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs: ventilation, diffusion, and perfusion.

Detailed explanation-5: -The four steps of gas exchange are ventilation, pulmonary gas exchange, gas transport, and peripheral gas exchange. These processes describe how gas is inhaled, exhaled, exchanged at the alveoli, transported through the blood, and again diffused across cellular membranes in body tissues.